1. Field of Invention
The present invention relates, generally, to camshaft phaser systems and, more specifically, to locking phasers for camshaft phaser systems.
2. Description of the Related Art
Conventional automotive camshaft timing systems (sometimes referred to as “variable valve timing” systems) known in the art typically include an internal combustion engine that has a crankshaft and one or more camshafts controlled by one or more camshaft phasers. Phasers are used to alter the timing of valve events so as to improve engine performance, fuel economy, and emissions. Phasers are typically operatively attached to an end of the camshaft and are also in rotational communication with the engine crankshaft, so as to either advance or retard the phase of the camshaft with respect to the crankshaft. Phasers can be actuated in a number of different ways, and have historically been controlled using servo-controlled hydraulic pressure. However, the recent trend in the art is to control phasers with electric motors, which can provide broader phase control and improved response time. The electric motor and phaser are operatively attached to each other and in rotational communication so as to allow rotation of the electric motor to adjust the phase angle of the camshaft. The electric motor is typically controlled by an engine control unit (ECU), which also controls fuel delivery and ignition timing.
Electric motors used with camshaft phasers known in the art are typically brushless DC electric motors, which provide longer life, better control, and faster response than conventional brushed DC electric motors. To that end, phasers driven by electric motors are better able to optimize the phase of the camshaft so as to provide increased engine performance and response, as well as improved emissions. To cooperate with the electric motors, phasers known in the art may include a friction-based locking mechanism to lock (or, “park”) the phaser in one or more optimal pre-determined positions, depending on vehicle and engine operating conditions.
Each of the components of a camshaft phaser system of the type described above must cooperate to effectively control the phase angle of the camshaft. In addition, each of the components must be designed not only to facilitate improved performance and efficiency, but also so as to reduce the cost and complexity of manufacturing and assembling the system. While camshaft phaser systems known in the related art have generally performed well for their intended purpose, there remains a need in the art for a camshaft phaser system that has superior operational characteristics, and, at the same time, reduces the cost and complexity of manufacturing the components of the system, as well as the overall dimensions of the various components.